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JEE Advanced Physics Electrostatics 2024 JEE Advanced 2024 (Paper 2)

JEE Advanced Physics Question (2024) — Solution

Question

A small electric dipole p _0, having a moment of inertia I about its center, is kept at a distance r from the center of a spherical shell of radius R. The surface charge density is uniformly distributed on the spherical shell. The dipole is initially oriented at a small angle as shown in the figure. While staying at a distance r, the dipole is free to rotate about its center. If released from rest, then which of the following statement(s) is(are) correct? [ _0 is the permittivity of free space.]

Options

  1. A. The dipole will undergo small oscillations at any finite value of r.
  2. B. The dipole will undergo small oscillations at any finite value of r>R.
  3. C. The dipole will undergo small oscillations with an angular frequency of 2 p_0 _0 I at r=2 R.
  4. D. The dipole will undergo small oscillations with an angular frequency of p_0 100 _0 I at r=10 R.

Answer

D. The dipole will undergo small oscillations with an angular frequency of p_0 100 _0 I at r=10 R.

Step-by-step solution

\( aligned & =| p E | \\ & I =p_0 E \\ & = p I ( 1 4 _0 4 R^2 r^2 ) \\ & = ( p 0 R^2 I _0 r^2 ) \\ & = p 0 R^2 I _0 r^2 aligned \) For \(r=2 R\) \( = p_0 4 / _0 ( C \) is incorrect \()\) Also, for \(r=10 R\) \( = p_0 4 l(100) \) (D is correct) It will oscillate for any finite value of \(r>R\). (B is correct)

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